Diesel Particulate Filters: Frequently Asked Questions
Our experts respond to common questions about diesel particulate filters, and explain when you need to seek servicing for your vehicle’s DPF
- Passive – Occurs automatically during consistent high-speed driving (like motorways) when exhaust heat naturally gets high enough.
- Active – Triggered by the vehicle’s computer when passive regeneration isn’t enough, often by injecting extra fuel to raise temperatures
- Forced – A manual process using diagnostic equipment to initiate regeneration when the filter is heavily blocked, often done by a qualified mechanic.
How often should I clean my DPF?
The ideal cleaning frequency really depends on how you use your vehicle. If you regularly take short trips or do high mileage, your DPF may need attention a little more often. Staying on top of cleaning helps keep your engine running smoothly and prevents avoidable blockages.
Can a DPF be cleaned if the warning light is on?
Yes — a warning light simply means your DPF is beginning to clog. We can safely and effectively clean it even when the light is on. If needed, we’ll also carry out diagnostics to make sure there aren’t any hidden issues contributing to the problem.
How long does DPF cleaning take?
Cleaning time depends on how blocked the filter is. A simple regeneration may only take a few hours, while a deeper clean can take up to a day. We’ll always give you a clear estimate before we begin, so you know exactly what to expect.
Will DPF cleaning save me money?
Definitely. Regular DPF cleaning helps avoid costly repairs, improves fuel efficiency, and keeps your vehicle performing at its best. A bit of preventative care goes a long way in protecting your engine and your wallet.
What is a Diesel Particulate Filter (DPF)?
A DPF is a built-in filter designed to capture and store soot from your vehicle’s exhaust, helping reduce harmful emissions. It routinely burns off this soot through a process called regeneration, helping the system stay clean and efficient.
What causes a DPF to become blocked?
Blockages usually happen due to frequent short trips, low-speed driving, poor-quality fuel, or engine issues that interrupt normal regeneration. With the right driving habits, most blockages can be avoided. If your DPF keeps blocking, it usually indicates an underlying fault that needs diagnosing and fixing, not just cleaning the filter.
How do I know if my DPF is blocked?
Common signs include a DPF warning light, reduced power, increased fuel consumption, or harder starting. If you notice any of these, it’s best to have it checked sooner rather than later.
Can I drive with a blocked DPF?
It’s not recommended. Driving with a blocked DPF can put extra strain on the engine and lead to issues like turbo damage. Sorting the problem early prevents bigger, more expensive repairs.
What is DPF regeneration and how does it work?
Regeneration is the process your vehicle uses to burn off built-up soot in the DPF. It can happen naturally during steady motorway driving or be triggered automatically by the engine. Either way, it helps keep the filter clear and functioning properly.
How can I prevent DPF faults?
Simple habits help: take your vehicle on occasional longer journeys, regularly drive on highways for 20-30 minutes above 2,500 RPM to help the DPF regenerate, use good-quality diesel, and keep the engine well-maintained, always using low-ash, manufacturer-approved engine oil. Avoiding frequent short trips also gives your DPF a better chance to regenerate naturally. Address Warning Lights: Don’t ignore the DPF warning light; get it checked by a professional.
What should I do if the DPF warning light comes on?
Try driving at sustained motorway speeds for 15–30 minutes to allow the DPF to regenerate. If the light stays on afterwards, it’s best to have a professional check things over.
Can a DPF be cleaned or does it need replacing?
Most of the time, a professional clean is all that’s needed. Only severely damaged or fully saturated filters require replacement. We’ll always advise the most cost‑effective solution.
Is removing the DPF a legal option?
No — removing the DPF is illegal in the UK and results in MOT failure and potential fines. Keeping the DPF in place protects both your vehicle and the environment.
How much does it cost to fix a DPF fault?
Costs vary depending on the issue. A professional clean typically costs £100–£300, while a replacement—if needed—can exceed £1,000. Catching problems early helps keep costs low.
